<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>三列布局补充一</title>
  <style>
    #left,
    #center,
    #right {
      height: 300px;
    }

    #left,
    #right {
      width: 300px;
    }

    #left {
      background-color: #c9394a;

      float: left;
    }

    #center {
      background-color: green;

      margin-left: 300px;

      margin-right: 300px;
    }

    #right {
      background-color: #cccccc;

      float: right;
    }
  </style>
</head>

<body>
  <div id="left"></div>
  <div id="right"></div>
  <div id="center"></div>
</body>

</html>